Multiple-P450 Gene Co-Up-Regulation in the Development of Permethrin Resistance in the House Fly, Musca domestica

Insect Cytochrome P450 Database: An Integrated Resource of Genetic Diversity, Evolution and Function

Insects, the most numerous and diverse group of animal species on Earth, have important interactions with humans through providing resources, transmitting diseases and damaging agricultural cultivars. Cytochrome P450 monooxygenases (P450s) are one of the most important protein families in insects implicated in the endogenous metabolism and detoxification of xenobiotics, including allelochemicals, insecticides and environmental pollutants. To better understand the evolution and function of insect P450s and support the development and application of insecticides for pest control, an integrated bioinformatics platform is highly desirable. Here, we present the Insect Cytochrome P450 database (ICPD, http://www.insectp450.net/), which contains 66,477 P450s collected from public databases and predicted from the genomes of 682 insect species using a standardised bioinformatics protocol. Phylogenetic relationships between P450 genes are constructed for each species. The structures of all P450 proteins in the database are predicted using ESMFold, then visualised using WeView. Web services, such as BLAST, homogeneous modelling and molecular docking, are provided for determining the catalytic activities of P450 proteins. The ICPD will facilitate systematic investigations of the evolution and functions of the complete insect P450 complement, and represents a powerful tool for guiding insecticide design and application.

Insecticidal Activity of Fatty Acids From the Fruit Extract of Momordica cymbalaria Fenzl Ex Naudin, Has Insecticidal Activities on Mosquito Larvae

The fruit and other parts of Momordica cymbalaria are known to have medicinal properties. The study investigates the chemical composition and functional groups of M. cymbalaria fruits to assess the insecticidal potential of its bioactive metabolites. In silico approach was used to understand the mechanism behind the insecticidal nature of these metabolites. Ethyl acetate extract has 18 compounds, whereas 20 compounds were identified in methanol using gas chromatography-mass spectroscopy analysis. The extracts contain several functional groups, including alkanes, esters, carboxylic acids, amides and aromatic groups. The insecticidal bioassay using methanol and ethyl acetate extracts of M. cymbalaria on Aedes aegypti and Culex quinquefasciatus mosquito larvae shows that the LC50 value for A. aegypti was 65.7 ppm, for C. quinquefasciatus was 96.9 ppm and for ethyl acetate and methanol extract is 282.36 and 388.09 ppm. Molecular docking of secondary metabolites was performed with five insect proteins, namely, odorant binding protein (OBP), cytochrome P450 (CYP450), prophenol oxidase (PPO), arylalkylamine n-acetyltransferease (aaNAT) and sterol carrier protein (SCP). Results show that methyl 6-cis, 9-cis, 11-trans-octadecatrienoate has high binding affinity with sterol carrier protein (SCP-2) besides showing binding with other insect proteins. The data suggest that methyl 6-cis, 9-cis, 11-trans-octadecatrienoate has multiple insecticidal actions and may serve as a green insecticide.

Insect Resistance to Insecticides: Causes, Mechanisms, and Exploring Potential Solutions

Insecticides play a crucial role as the primary means of controlling agricultural pests, preventing significant damage to crops. However, the misuse of these insecticides has led to the development of resistance in insect pests against major classes of these chemicals. The emergence of resistance poses a serious threat, especially when alternative options for crop protection are limited for farmers. Addressing this challenge and developing new, effective, and sustainable pest management approaches is not merely essential but also critically important. In the absence of alternative solutions, understanding the root causes behind the development of resistance in insects becomes a critical necessity. Without this understanding, the formulation of effective approaches to combat resistance remains elusive. With insecticides playing a vital role in global food security and public health, understanding and mitigating resistance are paramount. Given the growing concern over insect resistance to insecticides, this review addresses a crucial research gap by thoroughly examining the causes, mechanisms, and potential solutions. The review examines factors driving resistance, such as evolutionary pressure and excessive pesticide use, and provides a detailed analysis of mechanisms, including detoxifying enzyme overproduction and target site mutations. Providing an analysis of potential solutions, it discusses integrated pest management, strategic insecticide rotation, and the use of new pest control technologies and biological agents. Emphasizing the urgency of a multifaceted approach, the review provides a concise roadmap for sustainable pest management, guiding future research and applications.

The Dual Resistance Mechanism of CYP325G4 and CYP6AA9 in Culex pipiens pallens Legs According to Transcriptome and Proteome Analysis

Mosquitoes within the Culex pipiens complex play a crucial role in human disease transmission. Insecticides, especially pyrethroids, are used to control these vectors. Mosquito legs are the main entry point and barrier for insecticides to gain their neuronal targets. However, the resistance mechanism in mosquito legs is unclear. Herein, we employed transcriptomic analyses and isobaric tags for relative and absolute quantitation techniques to investigate the resistance mechanism, focusing on Cx. pipiens legs. We discovered 2346 differentially expressed genes (DEGs) between deltamethrin-resistant (DR) and deltamethrin-sensitive (DS) mosquito legs, including 41 cytochrome P450 genes. In the same comparison, we identified 228 differentially expressed proteins (DEPs), including six cytochrome P450 proteins. Combined transcriptome and proteome analysis revealed only two upregulated P450 genes, CYP325G4 and CYP6AA9. The main clusters of DEGs and DEPs were associated with metabolic processes, such as cytochrome P450-mediated metabolism of drugs and xenobiotics. Transcription analysis revealed high CYP325G4 and CYP6AA9 expression in the DR strain at 72 h posteclosion compared with that in the DS strain, particularly in the legs. Mosquitoes knocked down for CYP325G4 were more sensitive to deltamethrin than the controls. CYP325G4 knockdown reduced the expression of several chlorinated hydrocarbon (CHC)-related genes, which altered the cuticle thickness and structure. Conversely, CYP6AA9 knockdown increased CHC gene expression without altering cuticle thickness and structure. P450 activity analysis demonstrated that CYP325G4 and CYP6AA9 contributed to metabolic resistance in the midgut and legs. This study identified CYP325G4 as a novel mosquito deltamethrin resistance factor, being involved in both metabolic and cuticular resistance mechanisms. The previously identified CYP6AA9 was investigated for its involvement in metabolic resistance and potential cuticular resistance in mosquito legs. These findings enhance our comprehension of resistance mechanisms, identifying P450s as promising targets for the future management of mosquito vector resistance, and laying a theoretical groundwork for mosquito resistance management.

Unveiling the Role of Two Rhodopsin-like GPCR Genes in Insecticide-Resistant House Flies, Musca domestica

Insecticide resistance in insects, driven by the overexpression of P450 enzymes, presents a significant challenge due to the enhanced metabolic detoxification of insecticides. Although the transcriptional regulation of P450 genes is not yet fully understood, G-protein-coupled receptor (GPCR) genes have emerged as key regulators in this process. This study is the first to associate GPCR genes with insecticide resistance in Musca domestica. We identified two key rhodopsin-like GPCR genes, ALHF_02706.g1581 and ALHF_04422.g2918, which were significantly overexpressed in the resistant ALHF strain compared to sensitive strains. Notably, both ALHF_02706.g1581 and ALHF_04422.g2918 were mapped to autosome 2, where critical but unidentified regulatory factors controlling resistance and P450 gene regulation are located. This supports our hypothesis that GPCRs function as trans-regulatory factors for P450-mediated resistance. Functional analysis using transgenic Drosophila demonstrated that overexpression of these rhodopsin-like GPCR genes increased permethrin resistance by approximately two-fold. Specifically, ALHF_02706.g1581 overexpression significantly upregulated the Drosophila resistance-related P450 genes CYP12D1, CYP6A2, and CYP6A8, while ALHF_04422.g2918 increased CYP6G1 and CYP6A2 expression, thereby enhancing insecticide detoxification in rhodopsin-like GPCR transgenic Drosophila lines. These findings suggest that these rhodopsin-like GPCR genes on autosome 2 may act as trans-regulatory factors for P450-mediated resistance, underscoring their critical role in insecticide detoxification and resistance development in M. domestica.

The P450-Monooxygenase Activity and CYP6D1 Expression in the Chlorfenapyr-Resistant Strain of Musca domestica L

The house fly Musca domestica L. is one of the most common insects of veterinary and medical importance worldwide; its ability to develop resistance to a large number of insecticides is well known. Many studies support the involvement of cytochrome P-450-dependent monooxygenases (P450) in the development of resistance to pyrethroids, neonicotinoids, carbamates, and organophosphates among insects. In this paper, the monooxygenase activity and expression level of CYP6D1 were studied for the first time in a chlorfenapyr-resistant strain of house fly. Our studies demonstrated that P450 activity in adults of the susceptible strain (Lab TY) and chlorfenapyr-resistant strain (ChlA) was 1.56-4.05-fold higher than that in larvae. In females of the Lab TY and ChlA strains, this activity was 1.53- and 1.57-fold higher, respectively (p < 0.05), than that in males, and in contrast, the expression level of CYP6D1 was 21- and 8-fold lower, respectively. The monooxygenase activity did not vary between larvae of the susceptible strain Lab TY and the chlorfenapyr-resistant strain ChlA. Activity in females and males of the ChlA strain exceeded that in the Lab TY strain specimens by 1.54 (p = 0.08) and 1.83 (p < 0.05) times, respectively, with the same level of CYP6D1 expression. PCR-RFLP analysis revealed a previously undescribed mutation in the promoter region of the CYP6D1 gene in adults of the Lab TY and ChlA strains, and it did not affect the gene expression level. The obtained results show that the development of resistance to chlorfenapyr in M. domestica is accompanied by an increase in P450-monooxygenase activity without changes in CYP6D1 expression.

Genetics, genomics and mechanisms responsible for high levels of pyrethroid resistance in Musca domestica

Insecticide resistance is both economically important and evolutionarily interesting phenomenon. Identification of the mutations responsible for resistance allows for highly sensitive resistance monitoring and allows tools to study the forces (population genetics, fitness costs, etc.) that shape the evolution of resistance. Genes coding for insecticide targets have many well-characterized mutations, but the mutations responsible for enhanced detoxification have proven difficult to identify. We employed multiple strategies to identify the mutations responsible for the extraordinarily high permethrin resistance in the KS17-R strain of house fly (Musca domestica): insecticide synergist assays, linkage analysis, bulk segregant analyses (BSA), transcriptomics and long read DNA (Nanopore) sequencing. The >85,100-fold resistance in KS17-R was partially suppressed by the insecticide synergists piperonyl butoxide and S,S,S-tributylphosphorothionate, but not by diethyl maleate nor by injection. This suggests the involvement of target site insensitivity, CYP-mediated resistance, possibly hydrolase mediated resistance and potentially other unknown factors. Linkage analysis identified chromosomes 1, 2, 3 and 5 as having a role in resistance. BSA mapped resistance loci on chromosomes 3 and 5. The locus on chromosome 3 was centered on the voltage sensitive sodium channel. The locus on chromosome 5 was associated with a duplication of multiple detoxification genes. Transcriptomic analyses and long read DNA sequencing revealed overexpressed CYPs and esterases and identified a complex set of structural variants at the chromosome 5 locus.

Up-regulation of CYP6G4 mediated by a CncC/maf binding-site-containing insertion confers resistance to multiple classes of insecticides in the house fly Musca domestica

Populations of many insect species have evolved a variety of resistance mechanisms in response to insecticide selection. Current knowledge about mutations responsible for insecticide resistance is largely achieved from studies on target-site resistance, while much less is known about metabolic resistance. Although it is well known that P450 monooxygenases are one of the major players involved in insecticide metabolism and resistance, understanding mutation(s) responsible for CYP-mediated resistance has been a big challenge. In this study, we used the house fly to pursue a better understanding of P450 mediated insecticide resistance at the molecular level. Metabolism studies illustrated that CYP6G4 had a broad-spectrum metabolic activity in metabolizing insecticides. Population genotyping revealed that the CYP6G4v1 allele harboring a DNA insertion (MdIS1) had been selected in many house fly populations on different continents. Dual luciferase reporter assays identified that the MdIS1 contained a CncC/Maf binding site, and electrophoretic mobility shift assay confirmed that transcription factor CncC was involved in the MdIS1-mediated regulation. This study highlights the common involvement of the CncC pathway in adaptive evolution, and provides an interesting case supportive of parallel evolution in P450-mediated insecticide resistance in insects.

Biological Fitness Cost, Demographic Growth Characteristics, and Resistance Mechanism in Alpha-Cypermethrin-Resistant Musca domestica (Diptera: Muscidae)

Musca domestica L., a pest of animals and humans, has developed resistance to alpha-cypermethrin, a pyrethroid insecticide commonly used to control medically important pests in many countries, including Saudi Arabia. We investigated the mechanism underlying the development of alpha-cypermethrin resistance and life history characteristics of alpha-cypermethrin-susceptible (Alpha-SS) and alpha-cypermethrin-resistant (Alpha-RS) M. domestica using the age-stage, two-sex life table theory, which is crucial for developing a future rational management strategy and minimizing the negative effects of alpha-cypermethrin on the environment. Our results showed that Alpha-RS M. domestica had a 405.93-fold increase in resistance to alpha-cypermethrin relative to Alpha-SS M. domestica. This increase in the resistance toward insecticide was attributed to metabolic enzymes, such as glutathione S-transferases, specific esterases, and cytochrome P450 monooxygenases. Furthermore, Alpha-RS M. domestica exhibited lower relative fitness (0.50), longevity, survival rate, life expectancy, reproductive values, intrinsic rate of increase, net reproductive rate, fecundity, maternity, and finite rate of increase, along with shorter larval, female preadult, and adult durations than Alpha-SS M. domestica, indicating fitness costs associated with most parameters. However, no significant differences were found between the strains in the following parameters: egg, pupa, and male preadult durations; adult preoviposition, total preoviposition, and oviposition periods; female ratio; and total generation time. Additionally, Alpha-RS M. domestica had a markedly lower intrinsic rate of increase, net reproductive rate, and finite rate of increase than Alpha-SS M. domestica. The results of this study suggest that alpha-cypermethrin resistance may lead to dominant fitness costs in M. domestica. Overall, these findings will aid in the development of rational control strategies for M. domestica as well as help to reduce pesticide pollution.